Miracles in Dark Souls 2 are more or less support magic spells and consume faith pool instead of intelligence in case of Sorcery spells. You will be able to learn some high damage dealing miracles later in the game, but that doesn’t mean they aren’t effective.
As most of the offensive miracle spells are lightning based and lightning being the element that enemies are hardly resistant to, you can count on miracles to get you out of tough situations if the need be.
Though you will need a Sacred Chime to cast the Miracles. You can cast miracles on yourself, your weapon and your allies depending on the situation you are in.